apt-get update failing on ubuntu 17.10

[cruzer001]

I rechecked your sources.list trying to find something I missed, like a extra space or? Can't find anything wrong.

Code 503 usually means server side, could be busy/maintenance.

But when I try the URLs and they work for me.
http://us.archive.ubuntu.com/ubuntu/dists/artful (main, multi, and on)
http://security.ubuntu.com/ubuntu/dists/artful-security (main, multi, and on)

Still think you should try another source, just to cover all avenues. Easy to do in terminal.

Make a backup

sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

Switch to the main server

sudo sed -i 's/http:\/\/us./http:\/\//g' /etc/apt/sources.list

And update

I really don't have any other ideas

[jl2414]

I'm not a long-time user...

I have Ubuntu 16.04.
I recently started to use Terminal to update and I receive the about the same message.
I use also the Software Updater program to further update. You can also use Ubuntu Software navigate to Updates and update.

More I cannot tell you.

I hope a more longtime user can give some more information...

[kris.armstrong]

This is just weird !!!! no change

I even for the heck of it tried changing dns servers.
Google DNS (8.8.8.8, 8.8.4.4)
OpenDNS (208.67.222.222, 208.67.220.220)

neither made a differnce.

krisarmstrong@ubuntu:/$ sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak[sudo] password for krisarmstrong: 
krisarmstrong@ubuntu:/$ sudo sed -i 's/http:\/\/us./http:\/\//g' /etc/apt/sources.list
krisarmstrong@ubuntu:/$ sudo apt-get update
Err:1 http://security.ubuntu.com/ubuntu artful-security InRelease
  503  Service Unavailable [IP: 91.189.91.26 80]
Err:2 http://archive.ubuntu.com/ubuntu artful InRelease
  503  Service Unavailable [IP: 91.189.88.161 80]
Err:3 http://archive.ubuntu.com/ubuntu artful-updates InRelease
  503  Service Unavailable [IP: 91.189.88.161 80]
Get:4 http://archive.ubuntu.com/ubuntu artful-backports InRelease [72.2 kB]
Get:5 http://archive.ubuntu.com/ubuntu artful-backports/main i386 Packages [1,504 B]
Get:6 http://archive.ubuntu.com/ubuntu artful-backports/main amd64 Packages [1,508 B]
Get:7 http://archive.ubuntu.com/ubuntu artful-backports/main Translation-en [668 B]
Get:8 http://archive.ubuntu.com/ubuntu artful-backports/universe i386 Packages [3,380 B]
Get:9 http://archive.ubuntu.com/ubuntu artful-backports/universe amd64 Packages [3,392 B]
Get:10 http://archive.ubuntu.com/ubuntu artful-backports/universe Translation-en [1,880 B]
Get:11 http://archive.ubuntu.com/ubuntu artful-backports/universe amd64 DEP-11 Metadata [4,712 B]
Get:12 http://archive.ubuntu.com/ubuntu artful-backports/universe DEP-11 64x64 Icons [2,717 B]
Fetched 92.0 kB in 11s (8,254 B/s)      
Reading package lists... Done
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/artful/InRelease  503  Service Unavailable [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/artful-updates/InRelease  503  Service Unavailable [IP: 91.189.88.161 80]
E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/artful-security/InRelease  503  Service Unavailable [IP: 91.189.91.26 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
krisarmstrong@ubuntu:/$

[tps-mail]

So, service unavailable usually means you can't connect to the 'service' being requested. Not 'host not found' or anything DNS related. You are obviously resolving the IP from the FQDN, so ignore DNS. It's working. From a command prompt, try running

telnet archive.ubuntu.com 80

I don't remember if telnet is installed by default. You may have to install it. If you get the server banner, you are good. I'll assume you get the server banner. Are you behind any kind of firewall or HTTP Proxy setup?